Signaling apparatus



1N VENTORS ATTORNEYS.

SKS@

Sept. 30, 1941.. c, E. LoMAx ET A1.

SIGNALING APPARATUS Filed Aprila?, 1959 Sele Cfof" Line SufC/y MGS NQ Q\ Patented Sept. 30, 1941 SIGNALING APPARATUS Clarence E. Lomax, Oak Park, and Arthur Bessey Smith, Evanston, Ill., assignors to` Associated Y Electric Laboratories, Inc., Chicago, Ill., a corporation ofDelaware Application April 27, 1939, Serial No. 270,390v

Claims,

The present invention relates to signaling apparatus and, more particularly, to improvements in connecting links of the character `utilized in establishing connections between the lines of a signaling or telephone system,

It is an object of the invention to provide a connecting link of the character indicated wherein the line connecting apparatus is arranged in `an improved manner to be controlled by an element which is exceedingly fast in its response to voltage changes and is substantially nonconductive.`

It is another object of the invention to provide an impulse repeating link arranged in an improved manner to include a pulsing device of nonmagnetic character which possesses great sensitivity to voltage pulses.

It is a further object of the invention to provide a line selecting switch adapted for use in a signaling or telephone system which comprises impulse responsive line selecting means arranged in an `improved manner to include a pulsing device of nonmagnetic character which is characterized by great sensitivity to voltage pulses.

In general, the objects as set forth above are attained in accordance with the present invention by providing in a signaling system, a connecting link which comprises apparatus for forwarding a connection routed to the link, and circuit means comprising a crystalline body formed of Rochelle salt or equivalent material` for controlling the call forwarding apparatus.` Two embodiments of the line connecting `link are disclosed, one thereof comprising an impulse responsive selector switch of the character used in automatic telephone systems and the other comprising an impulse repeater of the general type conventionally associated with heavily loaded rural lines terminating at a small rural community telephone exchange. In each of the two embodiments of the invention there is p rovideda pulsing device in the form of a body supported to permit. movement of at least a portion thereof, together with pulsing contacts, operative in response to movement of the body, for repeating, to an associated pulsing circuit, impulses transmitted to the link. This body is formed of crystalline material and, in s the preferred embodiment, is comprised of Rochelle salt. When properly `constructed and shaped, the body is movable in response to changes in voltage impressed between predetermined points thereof. The body as thus constructed is essentially a voltage responsive device, it `being substantially nonconductive and being exceedingly fast in its response to changes in the voltage impressed between the above-mentioned predetermined points thereof.

Further features of the invention pertain to the particular arrangement of the circuit elements whereby the pulsing devices of the respective embodiments of the invention are controlled and additional operating features are attained.

The novel features believedto `be characteristic of the invention are set forthwith particularity in the appended claims. The invention, both as to its organization and method of operation together with further objects and advantages thereof, will best be understood by reference to the specification taken in connection with the accompanying drawing, the single figure of which illustrates the invention in itsembodiment in an automatic telephone system.

In general,A the system illustrated in the drawing comprises a relatively small community automatic exchange which terminates a plurality of subscribers lines, two of which are indicated at II) and II as extending to the substations A and B, respectively. Although the line II is illustrated as having only one substation associated therewith, this line may be `of the multiparty type having a plurality of substations associated therewith, the apparatus provided at each of the other substations being arranged in the same general manner as that provided at the substation B. In orderv to establish connections between the lines, there is provided in the exchange automatic switching apparatus which includes a pair of line switches I2 and I3 individual to the lines Ill and I I, a selector switch I4 and a connector switch I5. The substation A associated with the line I0 is of the well-known common battery type of which several commercial embodiments are available. 'Ihe substation B, on the other hand, is of the local battery type. In the interests of simplifying `the disclosure, only that portion of the apparatus provided at the I substation B which is required inorder to explain the operation o f the invention has been illushated in the drawing. In brief, the apparatus provided at the substation B comprises a transmitter 2q, a receiver 2l, an induction coil 22 and a local battery 23; which circuit elements are arranged to be interconnected by meansV of a hook switch 24 which includes a switchhook 34 for supporting the receiver 2l when not in use. The substation further comprises a pulsing or calling device, of the well-known dial operated type, which includes pulsing springs 25 for transmitting switching control impulses over the line Il. In order to indicate the presence of incoming calls on the line Il, there is also provided at the Vsubstation B a signal device in the form of a The i'lnal selector or connector switches of the' exchange are all of identical arrangement. brief, the connector switch I comprises a plurality of bank contacts arranged in levels and terminating the conductors of certain of the subscribers lines; a wiper carriage structure including the wipers |66 to |68, inclusive; means comprising a vertical magnet |24 for elevating the wiper carriage structure to bring the wipers v opposite a desired level of contacts; means comprising a rotary magnet |51 for rotating the indicated wipers until `they engage a .desired set of contacts in a selected level; a release magnet IIB; two sets of off-normal springs |66 and IIS; and a plurality of control relays constructed and arranged in the manner illustrated. More particularly, the `-control relays of the connector switch I5 include a `back-bridge relay RI D0, a line relay RIIG, a pair of slow-to-release hold relays Ril and RIZ, a slow-to-release digit transfer relay RI25, a slow-acting ring cut-off relay RISG, a busy test relay RI35, a slow-torelease pulse responsive relay RI and a slow- 13o-operate line switching relay RISE. The control apparatus ofthe connector switch further comprises a pulsing device which includes an elongated piezo-electric, crystalline body |60, preferably formed of Rochelle salt crystal. This body is xedly mounted at points adjacent one end vthereof upon a suitable base structure IBI. More particularly, the body I is constructed and connected in circuit in the manner disclosed in Patent No. 1,802,782, Sawyer, granted April v28, 1931. 'I'he elongated body |60, when constructed-of material of the character described, is substantially nonconductive and is characterized by the property of movement of the free end thereof in response to changes inthe voltage impressed across predetermined points thereof.

Movement of the free end of the body |60 Vis transmitted through an Vinsulating button |64 to an armature |65 which controls pulsing contacts included in pulsing circuits traced hereinafter for respectively energizing the vertical and rotary magnets |24V and |51. The arrangement of the circuit elements is such that the voltage of the exchange battery II'I is normally impressed between predetermined points or surfacesof the crystalline body |60 over a circuit which serially includes the windings of the line relay RI I0, and a pair of electrodes |62 and.v |63 adhesively secured to opposite surfaces of the body |60. The electrodes |62 and |63 are bonded or otherwise secured to thesurfaces of the body |60 which stations associated with the multiparty lines of the system. Since this apparatus may be of conventional construction and the arrangement thereof forms no part of the present invention, it has not been illustrated in the drawing.

AIn order to repeat to the automatic line selecting switches of the exchange impulses transmitted over the line II from one of the substations associated with this line, there is associated with the line an impulse repeating link I6. This link comprises a repeating coil 20|) and Vthree control relays RZIB, R220 and R230, the

first and second of which are of the slow-tolrelease type. The relay R230 is of the alternatabove and embodied in the connector switch I5.

More particularly, the pulsing device of the link I6 comprises an elongated piezo-electric crystalline body 2I3, preferably formed of Rochelle salt crystal, which is supported upon a base structure 2| l and includes a movable freeV end, the movement of which is transmitted to a pair of contact spring control armatures 2| 8 and 2I9 through an insulating button 2I'I. For the purpose of impressing the voltage of the exchange battery III between predetermined points of the body 2| 3, there are provided two electrodes 2I5 and 2I6 which are adhesively secured to the surfaces of the body which are substantially parallel to the major axis of the body.

Referring now to the operation of the system and considering first a call initiated at the substation A and intended for the substation B, the call is initiated in the usual manner by removal of the receiver provided at the substation A from its associated supporting hook or cradle, whereby a loop circuit including the two sides of the line I0 is completed between the substation Aand vthe line switch I2. The line switch I2 responds to the completion of this loop circuit by operating to select a trunk line extending to an idle one of the selector switches to which it has' access. Assuming that the selector switch I4, for example, is the rst available idle switch accessible tothe line switch l2, when the trunk line extending to the selector switch is tested and found to be idle, the line switch I2 operates to extend the calling loop circuit by way of the selected trunk line to the selector switch I4. In response to this operation, the control apparatus ofl the selector switch I4 is conditioned to respond to the impulses of the first digit of the `directory number Vdesignating the desired substation B and the usual' dial tone signal isreturned over the calling loop circuit to indicate to the calling party that the dialing operation may be started. In response to the impulses of vthe first digit dialed at the calling substation, the wipers ofthe selector switch I4 are elevated to a position opposite the level of band Vcontacts terminating the trunk lines extending to the group of connector switches including the switch I5. Whenthis first digit is dialed, the control apparatus of the selector switch I4 also operates -to terminate the dial tone signal. During the interdigit pause, between the flrst and second digits, the `wipers of the selector'switch I4 are automatically rotated inra well-known manner aast/:eee

a result, the free end of the body |160 is deilected successively to. test the condition` of the trunk lines; `terminating in the selected contact level.

Assuming, for example, that the. connector switch isthe rst available idle switch of the selected group, when the trunk lineextending to thisiconnector'switch is tested byl the selector switch I4 and found to be idle, the calling loop circuit is switched through to the indicated connector switch. When the .calling loop circuit is eX- tended `to `the connector switch I5, a relatively "l0 low resistance short-circuiting path comprising the calling loop circuitis completed for effectively short-circuiting the electrodes |62 and |63 of the pulsing device comprising the ,crystallinev body |60. This path may be traced as extending from the electrode |62 by `way of RAI 82, the upper side of the loop extending to the substation A, the bridge across the conductors of the line I0 at the substation A, the lower side of the calling loop circuit and RAIIJ4 to the electrode |63. By virtue` of the completionof this path, the magnitude of the voltage impressed between the electrodes |62 and |63 is determined by the resistance of the calling loop circuit. This voltage is decreased below the voltage of the exchange battery Ill by an amount equal to the voltage drop across the `windings ofthe line relay RI I0. Due to the decreased Voltage between the electrodes |62 and |63, the. free end. of the body |66 is caused to move downward to actuate the armature |65 `out of engagement with its associated upper contact and into engagement with its associated lower contact, thereby to prepare a circuit forenergizing the slow-to-release relay RIZEI. When the windings of the line relay RI I0 are energized over the. calling loop circuit, the Vline relay operates to complete, at RAI I I, an obvious circuit for energizing the slow-to-release relay RI I5. The relay RI I5, upon operating, completes the above- .mentioned circuit for energizing the slow-to- `release relay RIZB, this circuitextending from pressing ground potential upon the release conductor CIGS. At RAIZI, the relay RI connects the control conductor C|8`| of the trunk line incoming to. the connector switch I5 to ground, thereby to complete circuits, not shown, for maintaining the selector switch I4 and the line switch I2 operated. Following the operation of the relay RI26, the connector switch I5 is conditioned to respondv to the impulses of the second digit of the directory number designating the desired substation B.

During the impulses of the second and third digits dialed at the calling substation, the abovetraced low resistance path shunting the electrodes |62. and |63 is intermittently opened and closed.` The number of times this path is interrupted during a digit is, in each instance, determined by the numerical value of the digit. For example, if the second and third digits of the directory `number designating the desired substation B are five and six, respectively, the above-traced path will be interrupted five times during the second digit and siX times during the third digit. Each time this path is interrupted the relay RI I6 is deenergized and restores, and

`the full voltage of the exchange battery III is 'impressed' across the electrodes |62 and |63. As

upward so that the armature |65. is. moved out of engagement with its associated lower contact and into engagement with its associated upper contact. Thus, the pulsing contacts associated with the armature |65 are closed during theopen circuit portion of each impulse and are .disengaged during the closed circuit period ofreach impulse. virtue of the above-described `operation ofthe pulsing device, repeated to the verticalmagnet |24 over a circuit which iirstl extends from ground by way of RAI I6, the armature |65 and l its associated upper contact, RAI23, the` 011*- normal springs |28 and I2'I, the winding of `R125 and the winding of the magnet |24 tobattery.

In response to the intermittent operation of the magnet |24, the wipers |66 to |68, inclusive, are

stepped vertically to a position'opposite the level of bank contacts terminating thev link line extending to the repeater I6. At the beginning of the rst impulse when the relay RIIZE'Iv is iirst'energized, this relay operates to prepare, at RA |26, an alternative pulsing circuit including its'owfn winding and the winding of thevertical magnet |24. This alternative `pulsing circuit is completedwhen the wipers |66 to |68 are moved one step in the vertical direction, at which timethe OIT-normal springs |28 and |29 are closed and the off-normal springs |27` and |28 are disengaged. Speciiically, this alternative circuit extendsfrom ground by way of RAI I6, the armature |65 and its associated upper contact, RAI23, the ofi-normal springs |28 and |29, RAIiZBg' the Ywindirng of R|25 and the winding ofthe magnet |24 to battery. Due to the slow-to-release characteristics of the relays RI I5, RI2IJ and R|25,`al'l of these relays remain operated during the impulses oI the second digit. The oir-normal springs Ii|9 are closed to prepare a circuitfor energizing the release magnet ||8 in responseto the l-lrst vertical step taken by the wipers |66 te |68, inclusive. Shortly following the end of the second digit and during the interdigit pause between the second andithird digits, the relay RI25 restores RAI26 to open a point in the abovetraced alternative pulsing circuit and to prepare a circuit for energizing the relay R in parallel with the rotary magnet I5I.` This latter circuit is completed each time the pulsingdevice operatesduring the impulses of the third digit and may be traced as extending from ground by Way of RAII'S, the armature |65 and its associated upper contact, RAI23, theoif-normal springs |28 and |29, and Reina` te` RA|31 where it divides; one branch extending through the winding of RI48 to battery and the other branch extending by way of RAI55 and the winding of the magnet |57.` to battery. The relay R|46, upon operating in response to the initial-completion of thiscircuit, prepares, at RAI 4I and RAI 42, a test circuit including the winding of the busy test relay RI3S. At RAME, the relay RI 48 completes a path in multiple with the armature RA|3'|, thereby to prevent the impulsing circuit extending through the winding of the rotary magnet |51 from being interrupted through operation of the busy relay R|35 as the wipers |65 to. |68, inclusive, are moved over contacts terminating the conductors of busy lines. Due to the slow-torelease characteristics thereof, the relays RIIS, R|20 and RI4I| all remain operated throughout the third series of impulses. At the end of the last impulse of the third digit the wipers |66 vto |68,

inclusive, are moved intor engagement withthe The impulses of the second digit are, by

conductors terminating the link line extending toY therepeater I6, and this line is tested to deiterminethe idle or busy condition thereof. Assuming the called line to be busy at the time it is'selected, the busy test relayis energized over the `above-mentioned test circuit, which circuit extends by way of the grounded private conductor ofl the.v link line extending to the repeater I6, the wiper |61, RA|4I, RAIdZ and the winding of RI35', to battery. Upon operating, the relay VR|35 opens, at RAI31, a point in the initially traced circuit for energizing the relay RI40 and the rotary'inagnet |51 in parallel. At RAISE, the relay RI35 opens a point in the circuit traced `hereinafter for energizing the line switching relay RI50 and prepares a holding circuit for itself. ,This hol-ding circuit is -completed in response tothe release of the relay RIIIIl shortly 'following the end of the third digit and may be 4traced as extending from ground by way of RAIZI, CI01RAI36, RAIIiZ and the winding of .RI35 to battery. At RAI38, the relay RI35 completes alpath for conducting busy toner current .by way of the calling loopcircuit for the purpose of signaling the calling party that the desired connection cannot be obtained. This path may `partially-be traced as extending from one termi- ;nal of the busy tone source, not shown, by way ,ofC|58, the condenser |59 and RAI38 to the lower side of the calling loop circuit. Following ,the operation of the busy test relay RI 35i in the `man ner just explained, no further operation of thewapp'aratus occurs until the connection is cleared out at the calling substation. The man; ner in which the switch train is released when the calling subscriber replaces theV receiver provided at the substation A upon its supporting hook or cradleis explained hereinafter.

r 4 Assuming the called line II to be idle at the time it is selected, battery potential is present vupon the'private or control conductor of the ,link line extending to the repeater I6 so that thebusy test, relay RI35 is not energized over the previously traced test circuit. Shortly following the selection of the line, the relay RIIIII vrestores inthe manner pointed out above. Upon restoring, this relay completes, at RAIIII, the

Aabove-mentioned circuit for energizing the slowto-operate line switching relay RI50, this circuit .extending from ground by way of RAIZ I, RAI36,

the lower winding of RI 50, RA IIII, and the wiper |61 to the negative battery terminal as connected tothe private conductor of the link line extend ing to `the repeaterl I6 through the windings of the cut-off relay conventionally embodied in the 4line switch I3. When its lower windingis energized overthis circuit, the relay RI50 rst completes at the X contacts associated with RAI54 aholding circuit for itself, this holding circuit extending by way of the grounded release conductor CI06, RAI54V and the upper winding of RI50 to battery. Thereafter the relay RI50 opens, at, RAI55, apoint in the previously traced circuit for energizing the rotaryA magnet |51 and completes, at RAI53, an obvious path for impressing ground potential upon the private conductor of the link line extending to the repeater I6, thereby to mark the line I I as busy in the bank contacts of the other connector'switches having access to this line. At RAI52 and RAI 56, the relay4 R|50 completes a circuit for projecting ringing current 4over the link line extending to the repeater I6, thereby to energize the relay R230. ,This circuit may be traced as extending from one `terminal ;of the ringing current source, not

shown, byway 'of the interrupting contacts. of the ringing interrupter embodied in the exchange, the lower winding of R|30, RAI3I, RAISZ, the wiper'A |66, C169, the condenser 232, the windingof R230, RAZZI, C110, the wiper |68,

RAI56, RA|33, and the exchange battery to the opposite terminal of the ringing current source. This circuit is intermittently completed through operation of the ringing interrupter. Each time the' alternating current relay R230 is energized by current traversing this circuit it operates to complete, at RA23I, an obvious circuit for energizing the sloW-to-release relay RZIU. The relay VRZIII, in turn, operates its armatures RAZII and RAZIZ, thereby to connect the line conductors IIa and IIb to the conductors CI69 and CI10. In response to the last-mentioned operation, a

portion of the ringing current is shunted by way of the Vconductors of the line II through the windings 21 an-d 28 of the ringer 26 and the condenser 20. Accordingly, the ringer 26 is caused to operate to produce an audible signal indicating the presence of a call upon the line II. The relay RI50, upon operating, also cornpletes, at RAI5I, a path including the condenser |44 for shunting a portion of the ringing current by way of the calling loop circuit, whereby the usual ring-back tone signal is produced through operation of the receiver provided at the calling substation.`

In order to answer the call at the substation B, the' receiver 2| is removed from the switch.- hook 34. In response to this operation the hook switch 24 is operated to move the springs 30, 3|, 32 and 33 respectively into engagement. At the contact springs 30 an obvious local loop circuit,

including the battery 23, is completed for energizing the transmitter 20, thereby to render this transmitter operative to transmit voice frequency currents over the line I I. At the contact springs 3| and 32 the receiver ZI is bridged across the conductors or the line II, thereby to render this receiver operative to reproduce signal currents incoming to the substation B.v At the springs 32 and 33 a simplex circuit is completed for impressing the Voltage of the exchange battery II1 between the electrodes 2I5 and 2I6 of the pulsing device included in the repeater I6. Thus, the negative terminal of the exchange battery I1 is normally connected to the lower electrode ZIB and,.when the hook switch Z4 is operated, the positive or grounded terminal of the battery II1 is connecte-d to the upper electrode 2I5 over a path extending by way of the pulsing springs 25, the contact springs 33, the winding Z1, the conductor IIa, RAZII and the winding 20| to the electrode 2I5. A parallel path extends from ground by way of the pulsing springs Z5, the contact springs 33, the Winding 28, the Contact springs 32, the conductor IIb, RAZIZ and the vwinding 202 to the electrode 2I5. When the voltage of the current source II1 is thus impressed between the electrodes ZI5 and ZI6 the stress developed in the body ZI3 causes the free end of this body to be deilected downwardly, so that the contact springs associated with the armature 2I8 are closed and the contact springs associated with the armature 2I9 are moved into engagement. At the contacts associated with the armature ZIB, an obvious circuit is completed for energizing the slow-to-release relay R200, causing this relay to operate and disconnect, at RAZZI, the winding of the relayR230 from across the line conductors CI69 and C|10. Thus, the relays R230 and R2I0 are caused sequentially to restore in the order named. `At the contacts `associated with the armature 2|9 a loop circuit is completed for energizing the `lower windingof the ring cut-off relay RI30. AThis loop` circuit extends from 'ground by way of RAI33, RAISS, the wiper |68, CI'I0, the arma-` ture ,2|9, the winding 204, the resistor 205, the Winding '203, CIGS, the wiper |66, RAI52, RAI3I and the lower `winding of RI30 to the negative terminal `of the 'exchange battery. When this direct current circuit iscompleted the relay -RI3|l operates to complete, at the X contacts assoi ciated with RAI32, an obvious lcircuit `for energizing its upper winding. Thereafter, the relay R|30 completes its operation to open, at RAI3I and RAI33, two points in the 'above-.traced circuit for projecting ringing current over the link line extending to the repeater I6 and two points in its `own operating circuit. At RAI 3 I the relay RI30 also opens a point in the above-tracedpath for conducting a portion of the ringing current by `way of the callingloop circuit, thereby to terminate the ring-back tone signal. At RAI3I and RAI33 and their respective associated working contacts, the relay RI30 completes the desired conversational circuit `between the calling and calledsubstations and in so doing completes a circuit for energizing the back-bridge relay RI00. The lastementioned circuit extends from ground` through the lower winding of RI 'by way of RA'I33, RAISE, the wiper I68,\CI'I0, `the armature ZIB, the winding v204, the resistor' 205, the winding 203, CIGS, the 'wiper |66, RAI`52, RAI3I and the upper winding of RI 00 to battery. When energized over this loop circuit, therelay RI00 operates vits varmatures RAI02 to RAI05, inclusive, to reverse the direction of current flow over the calling loop `circuit in the usual manner. At RAII, the relay RI00 completes an obvious multiple path `for impressing ground potential upon the release conductor CIIlIA Y i L Thearra'ngement of the connector switch I5 is such that the release o'f a switch trainincluding this switch is entirely under the-control of the calling party. Thus, following thecomple'ti'on of the connection `between the calling substation A and the `called substation B, if the called party replaces the receiver 2| upon `the switch-hook 34. the above traced circuit for irnpressing the voltage ofthe source II'I `between the electrodes 2 I5 and 2I6 is interrupted, so that the body 2I3 assumes its normal position and the armatures EIS and :ZIB are operated 'to open the loop circuit'J extending through theV winding of the back-bridge relay RIG!! and to open the operating "circuit for the `slow-torel'e'ase relay R220. At the hook switch springs 30, the previously `described `local loop circuit including the battery 23 is interrupted. At the` springs 3| -and 32, thereceiver 2| is disconnected 'from across the conductors Vof the line II. The relay R220, upon restoring, reconnects the winding of the alternating current relay R230 across the line conductors CI69 and CI'IU. The back-bridge relay RI-00, `upon restoring, reverses the direction of current loWoVer the calling` loop circuit and at RAIOI disconnects multiple ground from the release conductor C406. When the: call is cleared out at the calling substation, the previously traced low resistance path shunting the electrodes |52 and i I 63 is interrupted with the result that the line relay RI I0 restores and the free end of the crystalline body |60 is denected upward to open at the armature l|65 the operat` ing circuit; rfor the relay RI20. Accordingly, the

relays RIIO, RIIS and VvR|2|l `are caused to restore inan obvious manner. i Upon restoring, the relay RII5 completes, at RAIII, the previously mentioned circuit `*for energizing the release magnet II8, vcausing the wipers I Eli to |68, inclusive, to :be returned to vertical and `rotary normal in a manner well understood in the art. When these wipers `'are restored to their respective normal 4positions the off-normal springs IIS are disengaged to open the operating circuit for the release magnet Hi8. The relayRIZ, upon restoring, ldisconnects the control conductor CIG'I and the release conductor CI06 from ground, thereby to initiate the release of the selector switch Ill and the line Vswitch I2 and to cause the restoration of the operated relays Ri() and RI-50. Duringl the release of the connector switch, ground potential yis removed from the private conductor of the link line extending to the repeater I5, therebyto mark the line II as idle in the bank contacts of the connector switches having access thereto. `Ground potential is similarly removedirom the private conductor of` the calling line ID -during the release of the loperated switches I5, I4 and I 2n Thus, the apparatus utilized -in setting up the connection is `fully released.` i

The `release of the switches I2, Id and I5 is effected in the `exact manner described above when the calling :party at the substation A is the first to `hang up, it being .pointed out that the back-bridge relay RI00 is deenergi-Zed and re` stores in response to operation of theV release magnet and when the wipers i6@ to I 63, inclusive, are moved out of engagement with the contacts terminating the `conductors of the link line eri-- tending to the repeater I-fi. In the event the called line II is busy at tlie time it is selected by the connector switch I5, the release of the switch train is effected when the calling party hangs up. In response to thispperation the calling loop circuit is interrupted.` to cause the reoperation of the pulsing device including the body and the sequential restoration `of the relays RIIIJ, Rlrl and Rl. The busy test relay is `releasedin response to the restoration ol.' the hold relay RI20. Otherewise, the switch train is released in the `manner previously `described.

Referring now to the operation of the apparatus to establish a connection between the substationsB land A on a call originating at the substation B, the `call is initiated by removing the receiver 2| from its supporting `hook Sil. In response tothis operation, the springs 30, 3|, 32 and `33 are respectively moved intoengageme'nt.

At the springs 32 and 33,the previously traced circuit is completed for impressing the voltage of the exchange battery II-'I between the electrodes 2I5 and 2| 8. As a result, the free end of the body 2 I3 is deflected downwardly to complete the vpreviously traced circuit for energizing the slow-to-release rel-ay R220. Upon operation, the relay R220 disconnects, at its armatures RAZZI, the winding of the alternating current relay R230 from across the line conductors CIGS and CI 10. At the contact springs associated with the armature 2I9 afloop circuit Iis completed which extends `from the repeating coil 200 to theline switch 243. This loop circuit may partially be traced as extending by way of CISB, the `winding 203, the resistor `205, the winding 204, the armature "2 I9 and the conductor CII0. In response to the completion of` this circuit, the line switch I3 operates to select an idle vone of the selector switches to which .it has access. Assuming that the selector switch I4 and the connector switch I are utilized in setting up the desired connection, these switches successively respond to the impulses making up the digits of the directory number designating the substation A. Thus, the selector switch I4, as selected by the line switch I3, responds to the impulses of the rst digit dialed at the substation B by operating to select the connector switch I5. The last-mentioned switch, in turn, responds to the impulses of the second and third digits by operating to select the calledline II1. During the dialing operation the impulses transmitted through operation of the pulsing springs 25 over the line II are repeated through operation of the pulsing device in the repeater I6 to the selector and connector switches I4 land I5, respectively. Thus, each time the springs 25 are opened, the abovetraced circuit for impressing the Voltage of the exchange battery II'I between the electrodes 2I5 and 2I6 is interrupted. As a result, the free end of the body 2I3 .is moved upwardly so that the contact springs associated with the armature 2I9 are opened to interrupt the loop circuit extending from the repeating coil 200 through the line switch I3. The contact springs associated with the armature 2I8 are also disengaged during each impulse Vto open the operating circuit for the relay R220, but due to its slow-to-release characteristic, this relay remains operated during impulsing. Aside from the manner in which the impulses are repeated to the switches I4 and I5, the connection is routed to the substation A in the exact manner set forth above with reference to the call routed to the substation B. Furthermore, the release of the connection is effected in substantially the manner described above when the callingparty replaces the receiver 2I upon its supporting hook 34. In response to this operation, the'hook switch springs 32 and 33 are disengaged to open the circuit for impressing the voltage of the exchange battery II1 between the electrodes 2I5 and ZI 6. Accordingly, the body 2I3 assumes its normal position to open, at the armatures ZIB and 2I9, the operating circuit for the relay R220 and the loop circuit extending to the connector switch I5, Ythereby to initiate the release of the switches I5, I4 and I3. When the relay R220 restores, the apparatus embodied in the repeater I6 is fully released.

While there have been described what are at present considered to be the preferred embodiments of the invention, -it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modications as fall within the true spirit and scope of the invention. Y

What is claimed is: 1. In a signaling system, a connecting link adapted for use in establishing connections between the lines of the system and comprising, in combination, a body supported to permit movement of at least a portion thereof, means for impressing a voltage between predetermined points of said body, means for shunting said predetermined points of said body, thereby to change the voltage across Vsaid predetermined points, said body being comprised of a material such that a portion of said body moves in response to changes in the voltage impressed between said predetermined points, and apparatus comprising circuit means controlled in accordance with the movement of said body for forwarding a connection routed by way of said link. 2. In a signaling system, a connecting link adapted for use in establishing connections between the lines of the system and comprising, in combination, a body supported at points adjacent one end thereof and having a free end, means for impressing a Voltage between predetermined points of said body, means for shunting said predetermined points of said body, thereby to change the voltage across said predetermined points, said body being comprised of a material such that the free end of said body changes its position in response to changes in the voltage impressed between said predetermined points,

and apparatus comprising circuit means controlled in accordance with changes in the position of said body for forwarding a connection routed by way of said link.

3. In a signaling system, a connecting link adapted for use in a connection extending between two lines of the system and comprising, in combination, a pulsing device comprising a body supported to permit movement of at least a portion thereof, means for impressing a voltage between predetermined points of said body, means comprising a pulsing circuit for intermittently shunting said points, thereby intermittently to change said voltage, said body being comprised of a material such that a portion of said body moves in response to changes in the voltage impressed between said predetermined points, pulsing contacts operative in response to movement of said body, and a pulsing circuit controlled by said contacts.

4. In a signaling system, a lconnecting link adapted for use in establishing connections between the lines of the system and comprising, in combination, a source of voltage, a line relay comprising a pair of windings, circuit means controlled by said relay, a pulsing device comprising a body supported to permit movement of at least a portion thereof, a circuit serially including said windings, said source and said body, whereby the Voltage of said source is normally impressed between predetermined points of said body, means comprising a pulsing circuit for intermittently shunting said device, thereby to cause the intermittent operation of said relay and intermittently to change the voltage between said predetermined points of said body, said body being comprised of a material such that a portion of said body moves in response to changes in the voltage impressed between said predetermined points, pulsing contacts operative in response to movement of said body, and a pulsing circuit controlled by said contacts.

5. In a signaling system, a connecting link adapted for use in establishing connections between the lines of the system and comprising, in combination, a source of voltage, an impedance element providing direct current paths and comprising a pair of windings for blocking the flow of audio frequency currents over said paths, apulsing device comp-rising a body supported to permit movement of at least a portion thereof, a circuit serially including said windings, said source and said body, whereby the voltage of said source is normally impressed between predetermined points of said body, means comprising a pulsing circuit for intermittently shunting said device, thereby to cause the intermittent operation of said relay and intermittently to change' the voltage between said predetermined points of said body, said body being comprised of a material such that a portion of said body moves in response to changes in the voltage impressed between said predetermined points, pulsing contacts operative in response to movement of said contacts, and a pulsing circuit controlled by said contacts.

6. In a signaling system, a connecting link adapted for use in establishing connections between `the lines of the system and comprising, in combination, a source of voltage, an impedance element providing direct current paths and comprising a pair of windings for blocking the ow of audio frequency currents over said paths, a pulsing device comprising a body of Rochelle salt supported to permit movement of at least a portion thereof, a circuit serially including said windings, said source and said body, whereby the voltage of said source is normallyimpressed between predetermined points of said body, means comprising a pulsing circuit for intermittently shunting said device, thereby to cause the intermittent operation of said relay and intermittently to change the voltage between said predetermined points of said body, said body being comprised of a material such that a portion of said body moves in response to changes in the voltage impressed between said predetermined points, pulsing contacts operative in response to movement of said contacts, and a pulsing circuit controlled by said contacts.

7. In a signaling system, a selector switch having a trunk line incoming thereto and comprising pulse responsive line selecting means, a pulsing device comprising a body supported to permit movement of at least a portion thereof, a source of direct current, an impedance element for con- -ducting current from said source to said trunk line and including a pair of windings for blocking the flow of audio frequency currents through said source, a circuit serially including said source, said body and said windings, whereby the voltage of said source is normally impressed between predetermined points of said body, means comprising a pulsing circuit extending by way of said trunk line for intermittently shunting said predetermined points of said body, thereby intermittently to change the voltage between said predetermined points, said body being comprised of a material such that at least a portion of said body moves in response to a change in the voltage between said predetermined points, pulsing contacts operative in response to movement of said body, and a pulsing circuit including said contacts for controlling said line selecting means.

8. In a signaling system, a selector switch having a trunk line incoming thereto and comprising pulse responsive line selecting means, a pulsing device comprising a body of Rochelle salt supported to permit movement of at least a portion thereof, a source of direct current, an impedancev element for conducting current from said source to said trunk line and including a pair of windings for blocking the flow of audio frequency currents through said source, a circuit serially including said source, said body and said windings, whereby the voltage of said source is normally termittently to change the voltage between said predetermined points, at least a portion of said body being movable in response to a change in the voltage between said predetermined points, pulsing contacts operative in response to movement of said body, and a pulsing circuit including said contacts for controlling said line selecting means.

9. In a signaling system, a selector switch having a trunk line incoming thereto and comprising pulse responsive line selecting means, a pulsing device comprising a body supported to permit movement of at least a portion thereof, a source of direct current, a line relay including a pair of windings providing paths for conducting current from said source to said trunk line, a slow-to-release hold relay controlled by said line relay, a circuit serially including said source, sai-d body and said windings, whereby the voltage of said source is normally impressed between predetermined points of said body, means comprising a pulsing circuit extending by way of said trunk line for intermittently shunting said predetermined points, thereby to cause the intermittent operation of said line relay and intermittently to change the voltage between saidpredetermined points, said body being comprised of a material such that at least a portion of said body moves in response to a change in the voltage between said predetermined points, pulsing contacts operative in response to movement of said body, and a pulsing circuit including said contacts for controlling said line selecting means.

10. In a signaling system, a selector switch having a trunk line incoming thereto and comprising pulse responsive line selecting means, a pulsing device comprising a body of Rochelle salt supported to permit movement of at least a portion thereof, a source of direct current, a line relay including a pair of windings providing paths for conducting current from said source to said trunk line, a slow-to-release hold relay controlled by said line relay, a circuit serially including said source, said body and said windingswhereby the voltageof said source is normally impressed between predetermined points of said body, means comprising a pulsing circuit extending by way of said trunk line for intermittently shunting said predetermined points, thereby to cause the intermittent operation of said line relay and intermittently to change the voltage between said predetermined points, at least a portion of said body being movable in response to a change in the voltage between said predetermined points, pulsing contacts operative in response to movement of said body, and a pulsing circuit including said contacts for controlling said line selecting means.

CLARENCE E. LOMAX. ARTHUR BESSEY SMITH. 

